Waterproof adhesive composition and method of making same



Patented Nov. 9, 1943 UNITED STATES WATERPROOF ADHESIVE COIWPOSITION ANDMETHOD OF MAKING SAME Edwin 0. Groskopi, Rutherford, N. 3. assignor toThe Patent and Licensing Corporation, New York, N. Y., a corporation ofMassachusetts Z'Claims. '(ci. 252-311.5\

This application is a division of my copending application Serial No.52,345, filed November 30, 1935, now Patent No. 2,180,305, datedNovember 14, 1939.

This invention relates to waterproof adhesive compounds and to methodsof manufacturing same and is concerned more particularly with adhesivecompositions of an asphaltic or similar bituminous character, or of arubber character.

The invention is more particularly concerned with adhesive compounds ofthe aforesaid character which can. be successfully employed underconditions which have heretofore presented considerable difficulty inthe attainment of the desired adhesive eifect.

One example of the particular. conditions untended to adhere.Furthermore, the requirement that the fllm shall resist flow attemperatures considerably above the melting point of the bitumencontained in, the emulsion, is also essential in order that theinsulating material remain in place and not move substantially from itsfixed position upon the metal layer under the heat of summertemperatures to which automobiles are subjected in use.

Bituminous emulsions of the aforesaid character which have heretoforebeen successfully used for said purpose, and possessing thecharacteristics just mentioned, are those made with the use of bentoniteor bentonite-like materials as the dispersing agent in accordance, forexample, with Kirschbraun Patent No. 1,620,899.

der which the adhesive compounds made in accordance with my inventionmay be successfully employed are those which prevail in the applicationof sound deadening sheets or pads to the metal parts of vehicle bodiesduring the course of manufacture of the vehicle.

Various forms and types of sound insulating sheets or pads have beenemployed in the automotive industry for deadening the sound of thevibrating metal parts of car bodies, the sound deadening sheet or padbeing attached, for. this purpose, to the inner surface of the metalparts, the vibrations of which it is desired to dampen. Thus, forexample, sheets or pads of relatively heavy porous or bibulousunsaturated felts, have been used for deadening the vibrational soundsof metal parts of car bodies. Sound insulating material of thischaracter has been successfully aflixed to the metal parts by theemployment of bituminous emulsions of those types in which a mineralcolloid constitutes the dispersing agent. It is essential, in the use ofan aqueous emulsion of bitumen or the like, for the purpose of afilxingthe sound deadening layer to the metal layer, that the emulsion be of acharacter such that when the water of the emulsion has been removed, theresultant adhesive film will not flow at temperature considerably inexcess of the melting point of the bitumen contained in the emulsion.This requirement of the adhesive is made necessary by reason of the factthat in the application of the sound deadening material to the metalparts of 'the body, the adhesive must be able to withstand flow at thetemperatures of the ovens through which the body of the car with thesound insulating material affixed thereto must pass, as otherwise thelayer of the sound insulating material will slide off or be otherwiseparted from the metal layer to which it is in While'emulsions of thistype have, as stated, been successfully used for cementing unsaturatedsheets or pads of fibrous felt to metal body parts, recent developmentsin the automotive industry have made it necessary to employ more or lessWaterproofed sound deadening materials, such as felts saturated tovarious degrees of waterproofness with asphalt, or the like.

In the use of these more or less waterproofed types of sound deadeningmaterial, however, considerable difiiculty has been encountered insuccessfully cementing the same with bituminous emulsions of thecharacter above described, to the metal parts of the body, under theconditions which necessarily prevail when this operation of amxing thesound deadening material to the metal parts must be performed. In. fact,in certain instances, the attempt to cement the more or less waterprooftype of sound deadening material to the metal parts of the body have metwith complete failure.

An object of the invention is to provide an improved form of compositionfor successfully cementing these types of materials to the metal p rtsof a body.

Another object of the invention is to provide an adhesive composition ofth character indicated which will at the same time possess thecharacteristics of resistance to flow under high heats which isobtained, as above stated, with the use of bituminous emulsions madewith bentonite or similar mineral colloids as the dispersing agent.

In approaching this problem, I found that the reason that bituminousemulsions of the character described may be successfully used as a.cementing medium for unsaturated sound-deadening felts, whereas they aretroublesome and in many instances completely unsatisfactory where a moreor less waterproof sound-deadening material such as saturated felt isused, is that in the former case the porous or bibulous character of theunsaturated felt is so comparatively great as to enable a sumcientportion of the water content of the emulsion to escape through the layerof sound deadening material itself before encoimtering temperaturessufficiently high to convert water into steam in the oven through whichthe body with the attached layer of sound insulating material must passin course of construction. Hence before encountering the water-boilingcase when considerably less than 90% ,1 .the water content thereof hasbeen eliminated, although this depends to some extent upon the rate atwhich the temperature-of the film is in-- creased. The film of thecomposition thus rapidly exerts a strong adhesive function due to thefact that the oily character of thesurface of felt saturated .withasphalt or the like is readily wetted by the composition which is itselfalso of temperature, the emulsion, in the first case, has

- ample opportunity to undergo sufilclent inversion or a sufilcientcoalescence of the bituminous-particles to render the film thereofadequately adheforth, applied to a layer ofmetal, and then resive andthereby prevent any steam that may be formed from blowing or otherwiseforcing the layer of insulating material away from the metal layer. Onthe other hand, where the insulating layer consists of more or lesswaterproofed material, a sufilcient amount of water to cause the film ofemulsion to invert and take on an adhe sive condition cannot escapebefore temperatures sufilciently high to convert water into steam arereached in the passage of the united materials through the ovens; andconsequently, at that stage, there is a lack of sufficient adhesionbetween the insulating layer and the metal layer, and the remainingwater entrapped between the two layers results in a blowing off orforcing away of the layer of insulatingmaterial from the metal layerwhen temperatures of the order of 212 F. are reached. In this connectionit may be noted that bituminous emulsions such as those made inaccordance with the aforesaid Kirschan oily character. This is in markeddistinction to the action of films of bituminous emulsion as ordinarilyproduced. This distinction can readily be observed by lightly pressing apad of saturated felt into a fihn of the ordinary type of bituminousemulsions of the character herein set moving the pad from the metallayer. The pad will show only water on the surface thereof thusindicating that the film of the emulsion has not wetted the surface of.the pad with anything more than water. On the other hand, when a.similar test is applied to the compositions made in accordance with myinvention, the removal of the pad from the metal layer will show thatthe parting takes place through the film of the bituminous portion ofthe composition, has selectively wetted the pad and adhered not only tothe surface of the metal, but to the surface of the removed-pad as-weu.

braun patent, and which provide a water-freewith my invention I havefound to be eminently satisfactory as a medium for cementing more orless waterproof insulating materials to the metal parts of car bodiesunder any of the aforesaid conditions of temperature and time of dryingto which they may be subjected during the conof the asphalt, togetherwith a material which will so act upon the emulsion system as to cause afilm thereof to invert and the particles of dispersed bitumen tocoalesce, enabling the film to take on a comparatively strong'ad'hesivetaharacter, while the water content of the film is stillsubstantially high. As a-matter of fact, in oertain embodiments of theinvention, the film of the composition may be caused to take on thiscondition when only as little as 20%, and in any As one illustration-ofan embodiment of the invention in a composition which meets therequirements hereinbefore set forth,'the following formula may be-given:

Parts Asphalt (51 to penetration) 56 Water 39 Bentonite (as dispersingagent) 2 Kerosene 3 Oxalic acid 0.02 ml acetate In the composition asrepresented by the above formula, the kerosene constitutes theactivating agent which causes the emulsion to invert and the dispersedparticles ofthe bitumen to coalesce while the film of the compositionstill contains substantial amounts of water, this action taking place inmany instances when as much as of the original water content of theemulsion is still present, although as heretofore stated, this may varywith the rate at which the water is driven ofi. The kerosene may beemployed in quantities varying from 3 to 10% by weight of the finishedproduct. Essentially, however, the activating agent must, in order toattain the objects of the invention, be of a character and be employedin quantities sufilcient to cause the film of the emulsion to take on acondition of inver ion or sumcient adhesive capacity to enable t to holdmaterial such as saturated felt to the metal surface to which it isapplied, without blowing ofi, during the conversion of the remainingportions of the water inthe film into steam when water boilingtemperatures are reached in the drying process.

In lieu of the kerosene as the activating agent specifically set forthin the above formula, other materials may be employed to function in the1 way in which the kerosene does. Thus for example, theactivating agentmay consist of relatively small amounts of-a solution of rubber in asolvent, or of a solution of certain gums and/or resins in a solvent;and in general, anyother substance which will not materially change thefluid character of the emulsion but will cause it ther 'reduced in size.

'to invert to the adhesive character specified, in

the presence of a much higher water content than if the activatingsubstance is omitted.

The purpose of the oxalic acid in the formula above given is to lowerand retain a lowered viscosity of the emulsion, while keeping it atsubstantially the same water content with which the emulsion isinitially produced (1. e., without requiring large additional quantitiesof water for the thinning), and thereby to facilitate the incorporationof the kerosene or other activating agent into the emulsion. Substancesother than oxalic acid, well known in the art for this purpose, may beemployed in lieu of the oxalic acid, to retain the liquid character ofthe product; or this effect may be induced in other ways known to theart.

The amyl acetate in the formula above given serves merely as a deodorantto disguise or obliterate the odor of the kerosene.

In the manufacture of the adhesive compositions in accordance with myinvention, as typi fied by the above stated formula, I prefer to proceedby first making a base emulsion of the asphalt or other waterproofmaterial in water with the aid of the bentonite or other emulsifyingagent suitable for the purpose, having in mind particularly therequirement that the water-free film of the emulsion must be capable ofresisting fiow at temperatures greatly in excess of themelting point ofthe dispersed material. The base emulsion as thus produced in accordancewith commercial practice in the art and containing approximately 37%water, 60% asphalt and 2 to 3% bentonlte, is one in which the particlesize of the dispersed asphalt averages about 18 microns. The emulsifyingtemperature for the production of the base emulsion will range fromapproximately 130 to 140 F. for asphalt of about the penetrationindicated.

The base emulsion as discharged ,from the emulsifying apparatus is thenpreferably cooled from the emulsifying temperature of 130 to 140 F. downto approximately 115 to 125 F., or a drop of approximately 15 F. Thethus cooled emulsion is then subjected to the action of a pugmill orsimilar beater after treating the emulsion with about 0.02% to 0.05% byweight of an electrolyte such as potassium dichromate. The purpose ofthis treatment with the electrolyte is to thicken or flocculate thecooled emulsion so that under the beating action of the 9118 11 theparticles of dispersed bitumen will be fur- This treatment of theemulsion is preferably such as to reduce the particle size of theemulsion to an average of about 7 microns. This greatly reduced averageparticle size also contributes to the ease with which the kerosene maybe incorporated in the emulsion without premature breaking thereof.

The emulsion with the reduced particle size is still comparatively thickdue not only to the fact that the water present must surround thegreatly increased amount of surface area of the increased number offiner particles, but also to the thickening effect of the electrolytepresent therein. In order therefore to thin out the emulsion of thereduced particle size and thereby facilitate the incorporation of thekerosene or other activating agent, the emulsion as discharged from thepugmill is then preferably cooled to a temperature of about 100 to 110F. and is then led into a second pugmill operating at a relatively highspeed, viz. of the order of 150 R. P. M. and the oxalic acid is trickledinto the emulsion in this pugmill while the emulsion is being agitatedat a high speed. The agitating action of the high Speed 1 118111111 aswell as the introduction of the oxalic acid serves to greatly thin theemulsion of reduced particle size without requiring any substantialadditional water. i

It will be appreciated that since the high speed pugmilling action andthe oxalic acid both serve to thin the emulsion, these expedients may beused more or less interchangeably with one another, depending upon theoperating conditions prevailing. which will determine the mosteconomical mode of bringing about the thinning of the emulsion.Furthermore where the thinning action is attained by the incorporationof a thinning agent, materials other than oxalic acid may be used forthis purpose in lieu of the oxalic acid.

After the emulsion with the reduced particle size has been thus greatlythinned in the manner described, it may be transferred to a separatemixing tank where the kerosene or other activating agent is added whilethe material is being stirred in the mixing'tank, the kerosene beinpreferably fed into this tank simultaneously with the feeding of theemulsion thereinto. Durin this incorporation of the kerosene or similar.

activating agent into the emulsion, it is quite essential that acomparatively low temperature be maintained and that, as already stated,the emulsion be of a thin consistency and have the particles thereof ina state of subdivision of the order of magnitude specified, in order toavoid inverting of the emulsion by the kerosene or other activatingagent With that in mind, it is desirable before feeding the emulsioninto the final mimng tank, to run into this tank about 50 to 100 gallonsof water per 2000 gallons of finished product. The effect of waterintroduced into the bottom of the tank before any of the emulsion is fedthereinto, is to greatly reduce the temperature of the emulsion, namelyfrom about to prevailing in the second pugmill to about 80 F.; and also,to further thin the emulsion.

The water in the bottom of the final mixing tank also prevents anymechanical friction during the mixing of the kerosene with the emulsion.The objective in this final step of the process is to incorporate thekerosene in the emulsion in the form of final droplets of the keroseneuniformly dispersed in the aqueous phase of the emulsion. This result isattained by conducting this step of the process in the manner described,it having been found that by having the emulsion very thin and theasphalt particles in the emulsion very finely divided, any tendency forthe emulsion to break upon the addition of the kerosene can be avoided.This danger of breaking of the emulsion is further minimized by reasonof the fact that the additional quantities of water placed in the bottomof the mixing tank as aforesaid, prevents any substantial rubbingcontact between the kerosene and the dispersed asphalt particles, whichmight, by accumulating to a sufiicient extent, cause the emulsion tobreak during the introduction of the kerosene.

Having thus described the invention and the advantages thereof, it willbe evident to those parting from its scope as defined in the appendedclaims.

What I claim is:

1. A waterproof adhesive composition comprising an emulsion of between50 and 60% asphalt in water, about 2 to 3% of an emulsifying agentcomprising a mineral colloid oi the bentonite type, whereby to renderthe water free him of the emulsion capable of resisting flow attemperatures greatly in excess of the melting point of the asphalt, saidemulsion containing a small amount of oxalic acid in solution in theaqueous phase, and also containing 3 to 10% of kerosene, by weight ofthe final composition, dispersed as -flne droplets in the aqueous phaseof the emulsion whereby to cause the emulsion to invert and thedispersed particles of a film thereof to coalesce when the film stillcontains from 20 to 90% of its original water content.

2. The method of producing a composition suitable for use as an adhesivein cementing layers of waterproof felt to the vibrating metal parts ofcar-bodies, which comprises emulsifying between 50 and 60% of bitumen inwater with the aid of about 2 to 3% or bentonite as a dispersing agentand under conditions such that the dispersed particles of the bitumenwill be or an average size of about '1 microns and the emulsion will beof substantially viscid consistency, then greatly thinning the emulsionwithout adding any additional substantial quantities of water by pug-

